FSO for High Capacity Optical Metro and Access Networks

With rapid development of cloud services, real-time video, and online social networks, there occurs an urgent requirement of transmission capacity for optical metro and access networks. The network operating at 100 Gb/s or 400 Gb/s has drawn significant research efforts as well as standardization activities, such as the IEEE 802.3bs 400G Ethernet Task. Compared with other modulation formats, PAM-4 has advantages of low cost, free of digital to analog converter (DAC), and easy implementation. In this work, we propose nonlinear digital signal processing in metro and access networks. We experimentally demonstrated 4x28Gb/s C-band directed modulated laser (DML)-based metro network over 160-km fiber transmission. We also experimentally demonstrate, for the first time, 2 × 64 Gb/s O-band PAM-4 signal transmission over 70 km SMF using DMLs with a bandwidth of 18 GHz. The sparse Volterra filter (SVF) is also proposed to compensate the transmission impairments with substantial computational complexity reduction.

Optical Switching Networks describes all the major switching paradigms developed for modern optical networks, discussing their operation, advantages, disadvantages and implementation. Following a review of the evolution of optical WDM networks, an overview of the future trends out. The latest developments in optical access, local, metropolitan, and wide area networks are covered, including detailed technical descriptions of generalized multiprotocol label switching, waveband switching, photonic slot routing, optical flow, burst and packet switching. The convergence of optical and wireless access networks is also discussed, as are the IEEE 802.17 Resilient Packet Ring and IEEE 802.3ah Ethernet passive optical network standards and their WDM upgraded derivatives. The feasibility, challenges and potential of next-generation optical networks are described in a survey of state-of-the-art optical networking testbeds. Animations showing how the key optical switching techniques work are available via the web, as are lecture slides (www.cambridge.org/9780521868006).

PON versus AON: Which is the best solution to offload core network by peer-to-peer traffic localization

In this PhD dissertation multi-rate models are examined for the performance analysis of telecommunication networks through mathematical analysis and simulation. Particular emphasis is given to optical networks. The main goal is the development of analytical models for the calculation of network performance metrics, such as blocking probabilities, transmission delay and utilization of the common channel. The proposed analytical models are distinguished according to the network technologies. Three different technologies are considered: A) Wavelength routed optical networks. B) Optical access networks. C) Wireless Internet access networks. Multi-rate loss models are proposed for the performance evaluation of wavelength routed optical networks. Firstly, the case of a single link is considered and then a mesh all-optical network is examined. In addition, analytical models are proposed for Optical Packet Switching (OPS) networks, for the case of an all-optical OPS switch and of an OPS mesh network. Multi-rate analytical models are proposed for the evaluation of the performance of Passive Optical Networks (PONs) implementing different multiple access methods. For the case of Time Division Multiple Access (TDMA) the Ethernet PON is studied, which supports multiple service-classes. Regarding the Wavelength Division Multiplexing (WDM) PONs a hybrid WDM-TDMA PON is considered and the call-level performance is evaluated. Calls are distinguished by their arrival process, which can be random or quasi random, by their bandwidth requirements, which can be fixed of elastic and by their behavior during their service, which can be calls of fixed transmission rate or calls that alternate between ON and OFF periods. Finally multi-rate loss models are proposed for the case of Optical Code Division Multiple Access (OCDMA) PONs that take into account the user activity and the presence of additive noise in the transmission channel. For the performance analysis of wireless Internet access networks analytical models are proposed, which implement the IEEE 802.11 protocol or the IEEE 802.11e protocol. The proposed analysis calculated the saturation throughput and the end-to-end packet delay as a function of the Medium Access Control (MAC) delay and the queueing delay. In all cases the accuracy of the proposed models is validated through simulation.

A coherent radio over fiber (RoF) system based on optical single-sideband modulation with no optical carrier (OSSB) for ultradense wavelength division multiplexing passive optical networks (UDWDM-PONs) is proposed and experimentally demonstrated. For one channel of the UDWDM-PONs, at the transmitter, the OSSB RoF signal is generated using a dual parallel Mach–Zehnder modulator (DP-MZM) with a real-valued precoded microwave vector signal which is applied to the DP-MZM via the two electrodes with one having a 90° phase shift. Then, the OSSB RoF signal is sent to a coherent receiver over a single-mode fiber (SMF). The coherent receiver with a free-running laser source as a local oscillator (LO) is used to perform the coherent detection. To recover the standard microwave vector signals from the real-valued precoded microwave vector signal that is embedded in a strong phase noise introduced by both the transmitter laser source and the LO laser source, a digital signal processing algorithm is developed to perform phase noise cancellation. An experiment is performed. The transmission of a 1.25-Gbps quadrature phase shift keying, a 1.875-Gbps eight-phase shift keying (8-PSK), and a 2.5-Gbps 16 quadrature amplitude modulation (16-QAM) microwave vector signals with a channel spacing as narrow as 3 GHz over a 25-km SMF is experimentally demonstrated. For the transmission of the 2.5-Gbps 16-QAM microwave vector signal, the received optical sensitivity at forward error correction level over a 25-km SMF link is −24.8 dBm, while for the 1.875-Gbps 8-PSK microwave vector signal, it can reach −29.8 dBm which leaves an enough margin to accommodate the splitting losses in the optical distribution networks.

A continual increase in bandwidth consumption stimulates the need for next generation optical access (NGOA) networks, which should also conform to the societal green agenda. Currently, the access segment consumes a major fraction (about 67%) of the energy consumption in end-to-end fiber-to-the-home (FTTH) based telecommunication networks, and thus the energy consumption of access networks remains a crucial concern. In this paper, we present a thorough analysis of energy consumption in various NGOA technologies. In this analysis, we have also accounted the effects of low power modes (e.g., sleep modes) and the use of optimal split ratios for the considered technologies on the energy consumption.

This paper outlines the issues in providing a seamless integration between energy-efficient optical access networks and metro networks that preserves the overall latency balance. A solution based on SDN is proposed and detailed. The proposed solution allows to trade the increased delay in the access section, due the utilization of energy efficient schemes, with a reduced delay in the metro section. Experiments in a geographically distributed testbed evaluate the different delay contributions.

This article presents, for the first time, the derivation of approximate analytical formulae for the probability density function and the cumulative density function of the optical signal-to-noise ratio variation in optical local and metropolitan area networks due to the weakly polarization-dependent gain of cascaded semiconductor optical amplifiers. The cumulative density function is used to calculate the outage probability and derive specifications for the maximum allowable value of polarization-dependent gain per semiconductor optical amplifier in order to achieve a given network size.

This book presents an in-depth deliberation on optical networks in four parts, capturing the past, present, and ensuing developments in the field. Part I has two chapters presenting an overview of optical networks and the enabling technologies. Part II has three chapters dealing with the single-wavelength optical networks: optical LANs/MANs, optical access networks using passive optical network architecture, SONET/SDH, optical transport network and resilient packet ring. Part III consists of four chapters on WDM-based optical networks, including WDM-based local/metropolitan networks (LANs/MANs) using single and multihop architectures over passive-star couplers, WDM/TWDM access networks as an extension of PONs with WDM transmission, WDM metro ring networks covering circuit-switched (using point-to-point WDM and wavelength-routed transmission) plus packet-switched architectures and WDM long-haul backbone networks presenting the offline and online design methodologies using wavelength-routed transmission. Part IV deals with some selected topics in six chapters. The first deals with transmission impairments and power-consumption issues in optical networks, while the next three chapters deal with the survivable optical networks, network control and management techniques, including GMPLS, ASON, and SDN/SDON, and datacenter networks using electrical, optical, and hybrid switching techniques. The final two chapters present elastic optical networks using flexible grid for better utilization of the optical-fiber spectrum and optical packet and burst-switched networks. The three appendices present the basics of the linear programming techniques, noise processes encountered in the optical communication systems, and the fundamentals of queuing theory and its applications in telecommunication networks. (238 words)

In terms of high-speed optical access system, an optical access network system with low-cost and low-complexity based on PAM8 modulated signal is proposed to meet the growing demand of optical access network capacity. Based on the system scheme proposed, an experimental simulation platform of 10 Gbit/s PAM8 modulated signal optical access system is built. In this scheme of the system, the intensity modulation/direct detection (IM/DD) is used to achieve the modulation and demodulation of the signal, and the entire optical access link does not use additional signal amplifier components, reducing the complexity and cost of the system. According to the experimental results, the BER of the received signal has slight changes within a certain transmission distance. And after 20 kilometers of transmission, when the BER of the received signal is close to 1e-4, the receiving sensitivity is lower than -12 dBm. The proposed optical access system has good sensitivity and has good application prospects for future broadband access network.

Optical access networks are envisioned to become increasingly complex as they support more and more diverse and immersive services, each with a different capacity, latency, and reliability need. While machine learning has been touted as a silver bullet that will intelligently manage network operations and resources to meet these demands, as it had been anticipated for core and metro networks, there exist various challenges that need to be addressed to progress machine learning models from research to production. In this tutorial, we first aim to motivate the continued push to advance optical access networks and rationalize the use of machine learning in these networks. We then highlight the challenges that are especially amplified due to the traffic dynamicity and heterogeneity, data scarcity, and computation-resource constraints of optical access networks. We discuss emerging machine learning approaches that are being explored to address these challenges. Finally, we consider a fast and self-adaptive machine learning enhanced dynamic bandwidth allocation scheme in an illustrative future use case of supporting immersive human-to-machine communications over the mobile fronthaul of next-generation mobile networks.

Liu YANG, Guoxin ZHENG, Qingfeng DING, Xing SUN Key Laboratory of Specialty Fiber Optics and Optical Access Networks, Shanghai University, China, E-mail: yangliu0806@126.com Key Laboratory of Specialty Fiber Optics and Optical Access Networks, Shanghai University, China, E-mail: gxzheng@staff.shu.edu.cn,398567216@qq.com Key Laboratory of Specialty Fiber Optics and Optical Access Networks, Shanghai University, China; School of Electrical and Electronic Engineering, East China Jiaotong University, China, E-mail: brandy724@sina.com

<div>Originally, networks were engineered to provide only one type of service, i.e. either voice or data, so only one level of resiliency was requested. This trend has changed, and today’s approach in service provisioning is quite different. A Service Level Agreement (SLA) stipulated between users and service providers (or network operators) regulates a series of specific requirements, e.g., connection set-up times and connection availability that has to be met in order to avoid monetary fines. In recent years this has caused a paradigm shift on how to provision these services. From a “one-solution-fits-all” scenario, we witness now a more diversified set of approaches where trade-offs among different network parameters (e.g., level of protection vs. cost and/or level of protection vs. blocking probability) play an important role.</div><div>This chapter aims at presenting a series of network resilient methods that are specifically tailored for a dynamic provisioning with such differentiated requirements. Both optical backbone and access networks are considered. In the chapter a number of provisioning scenarios - each one focusing on a specific Quality of Service (QoS) parameter - are considered. First the effect of delay tolerance, defined as the amount of time a connection request can wait before being set up, on blocking probability is investigated when Shared Path Protection is required. Then the problem of how to assign “just-enough” resources to meet each connection availability requirement is described, and a possible solution via a Shared Path Protection Scheme with Differentiated Reliability is presented. Finally a possible trade off between deployment cost and level of reliability performance in Passive Optical Networks (PONs) is investigated. The presented results highlight the importance of carefully considering each connection’s QoS parameters while devising a resilient provisioning strategy. By doing so the benefits in terms of cost saving and blocking probability improvement becomes relevant, allowing network operators and service providers to maintain satisfied customers at reasonable capital and operational expenditure levels</div>

Explosion of data and mass availability of Internet connections around the globe had created huge bandwidth requirements for bandwidth hungry applications. Despite the technological advances in the core and their ability to transport, still much work has to be done in the access networks in order to be able to let the broadband traffic be transmitted transparently. Current solutions for access networks do not provide a concrete solution for the famous last mile problem. In this review we will investigate optical access networks as viable solutions to the ongoing problems in the access networks. Further we will study physical and technological limitations with the current state-of-the-art optical technology. We will address the optical access networks promises in responding to these shortcomings. We will thoroughly study passive optical networks (PONs), reviewing different type of PONs considering their benefits and limitations. We will conclude our study with comparison of these current solutions.

Fiber optic amplifier is a field of new growing interest owing to its application to the optical metro and access networks for amplifying a weak optical signal. In order to design short-fiber-length and broadband optical amplifier, a new amplified fiber with semiconductor inner cladding has been presented. The semiconductor optical amplifier (SOA) is usually pumped by electric currents, but an optical pump is used to the semiconductor inner cladding fiber amplifier in our work. The rate equation is derived in the optical pumped amplifier, and the properties of the amplifier are analyzed. Comparison with conventional optical pumped amplifier, the semiconductor inner cladding fiber amplifier can be pumped by a wide-band optical pumped power, and high pump efficiency can be designed.